Catalysis is a change in the rate of a chemical reaction due to the participation of a material called a catalyst. Catalysts that speed the reaction are called positive catalysts. Catalysts that slow the reaction are called negative catalysts, or inhibitors. Unlike reactants, a catalyst is not consumed by the reaction itself.
A catalyst works by providing an alternative reaction pathway to the reaction product. The rate of the reaction is increased when this alternative route has a lower activation energy than the reaction route not mediated by the catalyst. Catalysts can also enable reactions that would otherwise be blocked or slowed by a kinetic barrier. The catalyst may increase reaction rate or selectivity, or enable the reaction at lower temperatures. As such, catalysts can be very valuable tools in industrial processes.
There can be drawbacks to the use of catalysts. For example, highly basic amines such as 1,8-Diazabicyclo-undec-7-ene (DBU) and Barton's base are among the most effective for uretdione/polyol catalysis. However, they are expensive and may contribute to an undesirable yellowing of the reaction product. In another example, tin compounds are used extensively in industrial products such as coatings, as catalysts for isocyanate/hydroxyl reactions. Because of concerns regarding the aquatic toxicity of some organotin compounds, there have been proposed regulations to ban organotin compounds from all coating applications.
It would be desirable to catalyze chemical reactions using methods and catalysts that overcome the drawbacks of the prior art.